Field
Example embodiments in general relate to a distally expanding facet implant with integrated plate and delivery device for distracting adjacent bony bodies, including adjacent vertebrae, and more particularly adjacent cervical vertebrae separated by a facet joint, while maintaining or improving cervical spine lordosis.
Related Art
Any discussion of the related art throughout the specification should in no way be considered as an admission that such related art is widely known or forms part of common general knowledge in the field.
Spine degeneration is a major burden to society. The current growth of the aging population is linked to a rise in cases of age-related spine joint degenerative change or arthropathy, which is a leading cause of chronic neck and back pain. The socioeconomic costs of degenerative spine disease are large. Such costs include both direct costs, such as payments for treatment of pain and neurologic disorders, and indirect costs from loss of work and frequent sick leaves.
The spinal column is composed of 33 vertebrae, separated by intervertebral discs and held together with ligaments and muscles. The spinal column provides an axial support for the human body in addition to its function as a protector to the spinal cord and its emerging nerve roots. Movement within each spine segment (two adjacent vertebrae) is facilitated by the anteriorly located intervertebral discs and two posterior facet joints. The series of these joints between adjacent vertebrae of the spinal column permit the complex flexible movements of the spinal column.
The aging process often leads to degenerative changes that impact the structure of the spine joints. The process involves dehydration of the intervertebral discs resulting in reduction of disc height. Subsequently, friction between the joint surfaces occurs and a process of degeneration and local inflammation begins. The joints then become stiffer and the ligaments become thickened and less elastic. The overall process is collectively named spondylosis. Spondylosis leads to reduction in the size of the neural foramens (the space where the nerves emerge from the spinal cord), disc herniation, and spinal stenosis resulting in axial neck and/or back pain and neurological compromise. As the degenerative changes advance and the intervertebral foramen narrowing progresses, compression of the nerve roots can occur leading to nerve damage. Such damage often manifests itself as numbness and weakness due to motor and sensory function loss in addition to persistent pain in what is called radiculopathy. Radiculopathy resulting from damage to the cervical nerve roots is referred to more particularly as cervical radiculopathy.
The main goal in treating radiculopathy is to decompress the affected nerve. This goal can be accomplished by direct nerve decompression and removal of the compressing element, or by distracting away from each other two adjacent vertebrae compressing the nerve. The two approaches are frequently combined. Typically, either an anterior procedure is performed that involves the removal of the collapsed intervertebral disc and replacement with a bone or synthetic cage, or a posterior procedure that involves laminectomy with or without facetectomy (facet removal). In either case, the procedure is often coupled with the addition of instrumentation between the involved vertebrae to stabilize them and facilitate their fusion together.
With respect to the cervical spine in particular, evidence has highlighted the importance of maintaining the natural cervical spine lordosis during surgical treatment of cervical radiculopathy as maintaining the natural lordosis is often associated with better neurological functional outcomes. Thus, surgical treatment of the cervical spine to counteract the effects of the degenerative process must incorporate cervical alignment to achieve the most beneficial outcome. While current anterior surgical procedures have been demonstrated to be effective in maintaining or restoring natural lordosis to the cervical spine, current posterior procedures have been associated with a worsening of lordosis, i.e. increased kyphosis.
At the same time, the current trend is to employ minimally invasive surgical approaches to treat various spinal diseases because such approaches have been demonstrated to lead to less post-operative pain, less surgical blood loss, and earlier recovery from surgery. For treatment of cervical radiculopathy, the commonly performed minimally invasive technique utilizes the posterior approach and specially designed devices to distract the facet joint by inserting an implant inside the facet joint and, consequently, relieving the nerve root compression. However, to date such devices have not achieved substantial success in providing optimal distraction of the facet joint while at the same time maintaining or restoring the natural lordosis of the cervical spine and avoiding inducing kyphosis.